Electrically driven aircraft cabin ventilation and environmental control system

ABSTRACT

The present invention relates to an electrically driven aircraft cabin and ventilation and environmental control system. The system includes at least one inlet for capturing ram air, an electrically driven compressor for pressurizing the ram air, and a thermal conditioning subsystem for thermally conditioning the pressurized ram air. The system further includes a subsystem for removing undesirable moisture from the thermally conditioned ram air.

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional PatentApplication No. 60/269,495, filed Feb. 16, 2001, entitled ElectricallyDriven Aircraft Cabin Ventilation and Environmental Control System.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to an electrically driven aircraftcabin and ventilation and environmental control system.

[0003] Many of today's aircraft use the extraction of thrust enginecompressor bleed air to power the aircraft cabin and cargo ventilationsystem and environmental control system (ECS). The extraction of enginecycle compressor core bleed air places a significant penalty on theengine cycle, reducing engine efficiency. Much of the power inherent inthe extracted bleed air is purposely wasted in the bleed air control anddistribution system to ensure that the hot bleed air conforms toaircraft material limits, before it is delivered to the ECS. Inaddition, the bleed air extraction and distribution equipment requiredto use engine bleed is expensive to purchase and install, and relativelyunreliable.

[0004] Modern aircraft ventilation systems fail to use the energycontained in cabin exhaust air efficiently. Conventionally, this air iscontinually dumped overboard. At high altitudes, this exhaust air hasuseable energy based on the pressure differential with ambient andenthalpy content. At lower altitudes, where the air pressuredifferential is not significant, this air may be a relatively cool heatsink.

SUMMARY OF THE INVENTION

[0005] Accordingly, it is a principal object of the present invention toprovide a system wherein aircraft onboard electric power is used to runthe cabin pressurization and ventilation system, and the environmentalcontrol system.

[0006] The foregoing object is attained by the electrically drivenaircraft cabin ventilation and environmental control system of thepresent invention.

[0007] In accordance with the present invention, an electrically drivenaircraft cabin ventilation and environmental control system comprisesmeans for capturing ram air, electrically driven means for pressurizingthe ram air, and means for thermally conditioning the pressurized ramair. The means for thermally conditioning the pressurized ram air mayutilize additional ram air and/or cabin exhaust air to carry out thethermal conditioning. The system further has a means for removingundesirable moisture from the conditioned stream.

[0008] A method for delivering conditioned air to an aircraft cabinbroadly comprises the steps of capturing ram air, pressurizing at leasta portion of the ram air with an electrically driven compressor,thermally conditioning the pressurized ram air, and delivering thethermally conditioned ram air to the aircraft cabin.

[0009] By employing electric power as the power source for the aircraftcabin ventilation and environmental control system rather than bleedair, the present invention contributes to the elimination of enginebleed equipment, as well as eliminating all the hot air, high pressurevalves and ducting of the pneumatic distribution system from the enginebleed system to the ECS.

[0010] Other details of the electrically driven aircraft cabinventilation and environmental control system of the present invention,as well as other objects and advantages attendant thereto, are set forthin the following detailed description and the accompanying drawingswherein like reference numerals depict like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a schematic representation of a first embodiment of anelectrically driven aircraft cabin ventilation and environmental controlsystem in accordance with the present invention;

[0012]FIG. 2 is a schematic representation of a second embodiment of anelectrically driven aircraft cabin ventilation and environmental controlsystem in accordance with the present invention;

[0013]FIG. 3 is a schematic representation of a third embodiment of anelectrically driven aircraft cabin ventilation and environmental controlsystem in accordance with the present invention;

[0014]FIG. 4 is a schematic representation of a fourth embodiment of anelectrically driven aircraft cabin ventilation and environmental controlsystem in accordance with the present invention; and

[0015]FIG. 5 is a schematic representation of a fifth embodiment of anelectrically driven aircraft cabin ventilation and environmental controlsystem in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0016] Referring now to the drawings, FIG. 1 illustrates a firstembodiment of an electrically driven aircraft cabin ventilation andenvironmental control system 100. In this system, ram air is broughtinto the system 100 through ram inlet 1. The inlet 1 may be located inany suitable position on an aircraft. A portion of the ram air isdiverted into conduit 2 for delivery to ventilation compressor 3 whereit is compressed. The compressor 3 puts into the ram air the energyrequired for both cabin pressurization and pneumatically driven airconditioning, depending upon environmental and flight conditions. Someof the heat of compression is removed from the ventilation compressorexit stream 34 in a secondary heat exchanger 4. The heat sink for theheat exchanger 4 is ram air obtained from the ram inlet 1 that is notdelivered to the compressor 3 and is instead diverted into the conduit5. On the ground, a ram air fan 15, connected to the ECS turbomachineshaft 35, provides the energy necessary to draw air through the system.The heat sink ram air delivered to the heat exchanger 4 is precooled bythe injection and evaporation of liquid water in the spray cooler 10. Aportion of the hot compressed ventilation air stream is removed upstreamof the heat exchanger 4 through line 29 to provide temperaturemodulation in the air cycle subsystem and air distribution system.

[0017] The cooled pressurized air is delivered to a conventional highpressure water separator air cycle subsystem via line 6. The air isadditionally cooled in a reheater heat exchanger 7 and then furthercooled in a condenser heat exchanger 8, where water vapor contained inthe air is condensed to liquid and separated from the cold air throughstream 9. This stream of liquid water is delivered to the spray cooler10, where it is injected into the incoming ram air stream to precool theheat sink for the secondary heat exchanger 4. The cold dry pressurizedair leaving the condenser 8 is delivered to the opposite side of thereheater 7 through line 11 where it is warmed in the reheater 7 as itcools the incoming air stream from the secondary heat exchanger 4. Thewarm, dry air is delivered through line 12 to the inlet of coolingturbine 13. Expansion of the cool pressurized dry air across the coolingturbine 13 reduces the pressure and temperature of the air. To controland moderate the outlet temperature of the cooling turbine air, hotbypass air 21 from another ECS pack aboard the aircraft is mixeddownstream of the exit 36 of the turbine 13. Work done by expansion inthe cooling turbine 13 is used along with primary power supplied by anelectric motor 14 to drive the ventilator compressor 3 and ram air fan15, which are on the same shaft as the electric motor 14 and the coolingturbine 13.

[0018] Cool dry air exiting from the condenser 8 is delivered throughline 16 to the cabin air distribution system mix manifold 17. In the mixmanifold 17, the cooled dry air is combined with similar coolconditioned air from other operating air cycle system packs via line 18,and with cabin recirculated air via line 19. During conditions whenoperation of the air cycle cooling system is not required to providecold air, the pressurized air stream 6 from the secondary heat exchanger4 is bypassed through line 20 directly to the mix manifold 17. The airin the mix manifold 17 is further conditioned by the addition of hotbypass air 22 as necessary to provide the desired cabin supply airtemperature. The conditioned cabin supply air is then delivered throughline 23 to the cabin 24. A portion of the cabin exhaust air 25 isrecirculated back to the mix manifold 17 with motion flow power providedby the recirculating fan 26. The remainder of the cabin exhaust air isexhausted to ambient through exhaust fan 27 and overboard line 28.

[0019] Referring now to FIG. 2, a second embodiment of an electricallydriven aircraft cabin ventilation and environmental control system 200is illustrated. As can be seen from this figure, system 200 retains thearchitecture of the system 100. In this embodiment however, instead ofexhausting the non-recirculated cabin air flow overboard, this air isdelivered through line 30 to recovery heat exchanger 31, where thecooler cabin air provides a heat sink for the hot ventilation compressorexit air, effectively precooling it prior to its delivery to thesecondary heat exchanger 4. The cabin air is then exhausted overboardthrough line 32. The use of this cool cabin air offloads the coolingload of the secondary heat exchanger 4, and therefore reduces the amountof ram air required, and its extraction penalty, to precool the aircycle system delivery air. This potentially results in a decrease intotal heat exchanger weight and aircraft drag.

[0020]FIG. 3 illustrates a third embodiment of an electrically drivenaircraft cabin ventilation and environmental control system 300 inaccordance with the present invention. This embodiment employs the basicarchitecture of the system 100 and the modifications of system 200. Inthis system however, after the cabin exhaust air has been used as a heatsink for the ventilation compressor exit air, the cabin air stream isexpanded across a power turbine 33. This is done to extract additionalenergy from the stream as a result of the differential between the cabinpressure and the ambient pressure and the enthalpy content of thestream. Power turbine 33 is preferably attached to the same shaft as theventilation compressor 3 and the cooling turbine 13, and its work isdelivered to the compressor 3 as shaft power to offset the electricalpower required at the motor 14.

[0021] A variation of the system of FIG. 3 involves using a singleturbine instead of two, essentially integrating the functions of boththe cooling turbine 13 and the power turbine 33. This single turbinewould perform the cooling turbine function for most of the flight, butat altitude, where the cooling turbine function is not necessary, itwould be used for energy recovery of cabin exhaust air. Only one ofthese functions would be performed under any given conditions, with thecooling function having priority over the energy recovery function.Thereby, through appropriate mode switching based on currentenvironmental conditions, the single turbine could perform eitherfunction as desired.

[0022]FIG. 4 illustrates yet another embodiment of an electricallydriven aircraft cabin ventilation and environmental control system inaccordance with the present invention. In this embodiment, the singlecooling turbine/high pressure water separator based air cycle subsystemloop is replaced with a condensing air cycle subsystem. In thisembodiment, the cool dehumidified air leaving the condenser 8 atintermediate pressure enters the condensing turbine 37, where throughfurther expansion the air is cooled and exits close to the desired cabinpressure level. This embodiment eliminates the need for hot air bypasstempering of the stream exiting the cooling turbine 13, as theconditions exiting the cooling turbine 13 are moderated by thecontrolled partial expansion of the air stream to give the desiredtemperature at the inlet of the condenser 8.

[0023]FIG. 5 illustrates yet another embodiment of an electricallydriven aircraft cabin ventilation and environmental control system inaccordance with the present invention. In this embodiment, theventilation compressor 3 and the air cycle subsystem are located on twoindependent shafts. One shaft would carry the ventilation compressor 3,the electric motor 14, and optionally the power turbine (not shown).Another shaft 38 would carry the cooling turbine 13, an electricgenerator 39, and a condensing turbine (not shown) if a condensing cycleis used. Energy flow (power) between the two subsystems would then betransmitted by an electric link 40 through power conversion hardware 41associated with the motor 14 and generator 39. The primary power for theventilation system compression and the ram air fan 15 is delivered bythe electric motor 14. This power is supplemented by the shaft powerdeveloped in the cooling turbine 13, and if appropriate, the shaft powerdeveloped by the power turbine 33 and/or the condensing turbine. Theelectric ECS turbomachine incorporates the cooling turbine and/or powerturbine, the electric motor, and/or generator, ventilation compressorand ram fan onto a single shaft, or onto two shafts. The motor and/orgenerator must operate at variable speed, therefore an inverter/motordrive and associated control functions will be required for each.

[0024] It is apparent that there has been provided an electricallydriven aircraft cabin ventilation and environmental control system whichfully satisfies the objects, means and advantages set forthhereinbefore. While the present invention has been described in thecontext of specific embodiments thereof, other alternatives,modifications, and variations will become apparent to those skilled inthe art having read the foregoing description. Therefore, it is intendedto embrace those alternatives, modifications, and variations which fallwithin the broad scope of the appended claims.

What is claimed is:
 1. An electrically driven aircraft cabin andventilation and environmental control system which comprises means forcapturing ram air, electrically driven means for pressurizing said ramair, and means for thermally conditioning said pressurized ram air.
 2. Asystem according to claim 1, wherein said electrically driven means forpressurizing said ram air comprises a ventilation compressor driven byan electric motor mounted on a shaft.
 3. A system according to claim 2,wherein said thermal conditioning means comprises heat exchanger meansfor removing heat from a flow of compressed air exiting said ventilationcompressor.
 4. A system according to claim 3, wherein said heatexchanger removing means comprises a secondary heat exchanger whichutilizes a portion of said ram air as a heat sink.
 5. A system accordingto claim 4, further comprising means for precooling said portion of saidram air utilized as said heat sink.
 6. A system according to claim 3,wherein said thermal conditioning means further comprises means forfurther cooling said flow of compressed air exiting said heat exchangermeans.
 7. A system according to claim 6, wherein said further coolingmeans comprises a reheater heat exchanger for cooling said flow ofcompressed air exiting said heat exchanger means and a condenser heatexchanger for condensing water vapor in said air exiting said reheaterheat exchanger.
 8. A system according to claim 7, wherein said thermalconditioning means further comprises means for heating said air exitingsaid condenser heat exchanger.
 9. A system according to claim 8, whereinsaid heating means comprises said reheater heat exchanger.
 10. A systemaccording to claim 8, wherein said thermal conditioning means furthercomprises a cooling turbine to reduce the pressure and temperature ofthe warmed air exiting said reheater heat exchanger.
 11. A systemaccording to claim 10, further comprising means for mixing engine bypassair with air exiting said cooling turbine.
 12. A system according toclaim 10, wherein said cooling turbine is mounted to said shaft.
 13. Asystem according to claim 10, wherein said cooling turbine is mounted toa second shaft.
 14. A system according to claim 13, further comprisingan electrical generator mounted to said second shaft and a powerconversion unit connecting said electrical generator and said electricmotor.
 15. A system according to claim 10, wherein said thermalconditioning means further comprises a mix manifold for receiving anexit air stream from said cooling turbine and for delivering air to acabin.
 16. A system according to claim 15, wherein said mix manifoldreceives at least one of recirculated air from said cabin, a portion ofsaid compressed air prior to said compressed air entering said heatexchanger means, and hot gas bypass air from an engine.
 17. A systemaccording to claim 16, further comprising means for exhausting a portionof cabin exhaust air to ambient.
 18. A system according to claim 16,further comprising a recovery heat exchanger for receiving said airexiting said compressor and means for delivering cabin exhaust air tosaid said recovery heat exchanger to act as a heat sink.
 19. A systemaccording to claim 18, further comprising a power turbine mounted tosaid shaft and said cabin exhaust air delivered to said recovery heatexchanger further being used to drive said power turbine.
 20. A systemaccording to claim 18, further comprising a condensing turbine mountedto said shaft and said condensing turbine receiving cool dehumidifiedair exiting said condenser heat exchanger and further expanding the airso that said air exits said condensing turbine close to a desired cabinpressure level.
 21. A method for delivering conditioned air to anaircraft cabin comprising the steps of: capturing ram air; pressurizingsaid ram air; thermally conditioning said pressurized ram air; anddelivering said thermally conditioned air to said aircraft cabin.
 22. Amethod according to claim 21, wherein said pressurizing step comprisingproviding an electrically driven compressor and introducing at least afirst portion of said captured ram air into an inlet of said compressor.23. A method according to claim 22, wherein said step of thermallyconditioning said pressurized ram air comprises providing a secondaryheat exchanger and introducing an outlet stream of air from saidcompressor into said secondary heat exchanger.
 24. A method according toclaim 23, further comprising cooling a second portion of said capturedram air and introducing said cooled second ram air portion into saidsecondary heat exchanger as a heat sink.
 25. A method according to claim23, providing a reheater heat exchanger and a condenser and furthercooling said pressurized ram air by passing an exit stream of air fromsaid secondary heat exchanger through said reheater heat exchanger andsaid condenser.
 26. A method according to claim 25, further comprisingwarming said air exiting said condenser by passing said air through saidreheater heat exchanger.
 27. A method according to claim 26, furthercomprising providing a cooling turbine, introducing said warmed airexiting said reheater heat exchanger into an inlet of said coolingturbine, and expanding said air introduced into said cooling turbineinlet.
 28. A method according to claim 27, further comprisingintroducing said expanded air exiting said cooling turbine into saidcondenser and delivering said expanded air in a cooled condition to acabin air distribution system mix manifold.
 29. A method according toclaim 28, further comprising mixing hot gas bypass air from an enginewith said expanded air prior to introducing said expanded air into saidcondenser.
 30. A method according to claim 28, further comprisingintroducing at least one of recirculated cabin air, hot gas bypass airand a portion of said air exiting said secondary heat exchanger intosaid mixing manifold.
 31. A method according to claim 30, furthercomprising exhausting cabin air overboard the aircraft.
 32. A methodaccording to claim 30, further comprising providing a recovery heatexchanger, introducing compressed air exiting said compressor into saidrecovery heat exchanger, and providing a cabin air portion as to saidrecovery heat exchanger for use as a heat sink.
 33. A method accordingto claim 32, further comprising exhausting said cabin air portion to theambient after its use as a heat sink.
 34. A method according to claim32, providing a power turbine to drive said compressor, introducing saidcabin air portion in a heated condition into an inlet of said powerturbine to drive a shaft on which said power turbine and said compressorare located, and exhausting an exit stream from said power turbine tothe ambient atmosphere.
 35. A method according to claim 28, furthercomprising providing a condenser turbine and passing said air streamexiting said condenser through said condenser turbine prior to saiddelivering step.
 36. A method according to claim 27, further comprisingmounting said compressor and an electric motor for driving saidcompressor on a first shaft, mounting said cooling turbine and anelectric generator on a second shaft, and transmitting energy flow byproviding an electric link between said electric motor and said electricgenerator.